The present invention relates to a packaging tray and, more particularly to a molded food packaging tray for use in packaging meats, fish, poultry and other comestibles in conjunction with a transparent overwrap film. The inventive packaging tray is provided with a novel peripheral lip structure which will aid in preventing the collapse or fracture of the tray side walls in view of pressures exerted by the overwrap film when applied to the tray in an automatic tray overwrap machine.
In many modern food retailing operations, such as in supermarkets, meat and produce markets and the like, there are customarily employed food trays molded from wood or paper pulp or from various plastic material, for instance, foamed plastic, for the display and packaging of meats, fish, poultry and other produce or comestibles. Generally these trays are relatively shallow rectangular flat-bottomed trays having outwardly inclined side walls, into which the commodities are placed, and thereafter a transparent material such as heat sealable cellophane or heat shrinkable or stretchable plastic film is tightly wrapped and sealed about the tray bottom to form an attractive retail package. This type of package is extremely neat in appearance, forms a protective arrangement for the commodity contained therein while allowing the prospective customers to view its contents, so as to greatly assist in the sale of the commodities.
Heretofore, the sealing of the commodity-containing tray with the transparent overwrap film was usually effected manually by generally unskilled or semiskilled labor. Although the packages obtained in this manner were, as a rule, satisfactory in their appearance and quality of sealing the commodities, the procedure was slow and cumbersome and not at all adapted to high-volume production demands.
More recently, there have been developed automatic tray overwrap machines which, at extremely high rates of speed, will cover and seal a tray containing a commodity, such as meat, fish, poultry or the like, with a transparent overwrap film of a suitable material as mentioned hereinabove. Although the automatic machines fulfill the demand for supplying wrapped trays of the type in question to a highly satisfactory degree, serious problems have been encountered in their use. Thus, the automatic overwrap machines when positioning or contacting the trays for contact with the overwrap film, and during the sealing of the film to the trays, are proned to impart relatively high forces to the sidewalls of the trays, thereby generating extremely high localized stresses which frequently cause to the tray side or end walls to buckle and fracture. This buckling may be the result of the inwardly directed forces exerted on the side walls of the tray due to impact by the machines and/or the tension formed by the overwrap film which is being applied to the trays.
Further basic causes of tray failure when the trays are overwrapped with transparent film in automatic machines may be ascribed to poor tray design for intended application thereof, in essence, inadequate side wall and tray bottom strength; incorrect design criteria in relationship between tray bottom and upright wall structures; design of automatic equipment, and the like.
To summarize, the typical failures of meat trays in automatic tray overwrap equipment relate to:
1. Bending or breaking at the sidewall to bottom radius due to the concentration of inward or outward bending moment forces at this point in that tray.
2. Distortion, folding or breaking of the trim lip due to the large contact area of the trim flange on the tray and the high coefficient of friction of the foam tray surface and the overwrap film surface.
3. Bowing of the trays when subjected to the wrapping forces in the equipment, and the related package instability through the remainder of the automated weighing/pricing/labeling equipment.